Nikon Fieldscope Digiscoping Eyepiece

I have a new Nikon 82mm ED Fieldscope with a variable zoom 25-75 power eyepiece. For digiscoping with my current setup (FSB-4 bracket and Nikon Coolpix P4 camera), I will need to purchase a Wide Digiscoping Eyepiece in either 30 power, 50 power, or 75 power. Other than the obvious magnification differences, what advantages/disadvantages would there be for having a 30X, 50X, or 75X eyepiece. I plan to use the digiscoping setup to photograph wildlife and would prefer to have a good overall eyepiece as each eyepiece is over $250 and most of them have been discontinued...

Thanks in advance!

I'd like to see some responses on this also.